Fats and oils are regenerative biogenous energy storages. In earlier times, bovine suet for example was only used as cooking fat or in the making of candles. Other animal fats like pig lard and bone fat were considered to be highly nutritional for the human diet. Biological waste fats of every kind were also considered, until very recently, as equally nutritional animal feed for the feedstock industry. Only with the epizootic problems of foot and mouth disease and BSE and the large amount of rendering fats that resulted thereof, did animal fats become more and more realistic as an energy source or diesel alternative.
Fats and oils are triglycerides, i.e., esters comprised of glycerine with various fatty acids, especially higher fatty acids. In general, only those fatty acids which contain more than 12 C-atoms are referred to as higher fatty acids. Normally, triglycerides bind one molecule of glycerine to three molecules fatty acids. Those fatty acids respectively which contain triglycerides vary widely and are dependent on the kind of fat used. In vegetable oils/fats, there are a predominant proportion of unsaturated and polyunsaturated fatty acids, i.e., oleic and linoleic acids. Saturated fatty acids such as palmitic acid play a less important role. In animal fats, the simple unsaturated fatty acids, chiefly oleic acid, and the saturated fatty acids, especially palmitic and stearic acid, predominate. This results in the high melting point of animal fats compared with that of vegetable oils.
Many accompanying substances of fats are not desired for technical utilization. These are to begin with ffa, diglycerides and monoglycerides and glycerine to some extent, which result from the hydrolysis of fats. Sterol, isoprenoid, phospho- and glycolipids are included in this group as well. Through autoxidation of the fatty acids, volatile components such as e.g., aldehydes, alcohols and ketones, and non-volatile components, are formed. The volatile components are mostly responsible for the displeasing aging odors from the fats/oils. The non-volatile components are odorless but accelerate the decomposition process. Also found predominantly in animal fats are heavy metals which the animals ingest through the food chain. This acts catalytically and contributes equally to further decomposition.
If fats or oils are burned and used as an energy source or a fuel substitute, then all of the accompanying substances mentioned, except for heavy metals, can be burned simultaneously, but this makes the handling of fat difficult. These substances shorten the storage-period, act negatively upon the exhaust gas composition and corrosively upon the motor assembly, hence making extensive cleaning measures in the utilization of animal fats unavoidable. The direct use of fat as fuel in diesel motors has already been mentioned in DE 31 17 374 A1. Because animal fats have a relatively high melting point, heating the fuel is imperative. Utilization is possible and relatively easy to realize. Long term attempts with diesel motor usage however displayed a major problem in animal fat use. Due to the high ffa concentration, maximum life expectancy is considerably limited. Especially components which are mechanically under high stress such as, for example, the entire injection system of modern diesel motors show wearing after a few hours of operation. This is why it is so astonishing that corrosion of the DE 196 22 601 C1 can be traced back to an excessively high proportion of glycerine, whereas used grease by comparison with an acidity of 75% can be expected to function trouble free in a diesel motor process. “The known damage mechanism” mentioned in this patent specification was not explained further therein and is in blatant contradiction to the analysis conducted by the declarant in connection with the subsequently illustrated invention, and to the analysis initiated by her and carried out by the specialized professional research facilities and well-known motor manufacturers. Such a usage as fuel must be doubted upon and can only lead to a financial loss for the user.
There exists a series of methods for preparing fats for motor processes. The fibril and heavy metals can be removed through ordinary washing with aqueous acid solutions. Phosphoric and citric acids are two such possible acids which are especially suitable and are already often utilized. Through such a washing process, the corrosive components, the fatty acids, are not removed. The possibility to remove fatty acids by washing with diluted sodium hydroxide exists. This method is only suited for fatty acids of low concentration. The common fats may contain 25 percent by weight fatty acids or more. This corresponds to a total acid number (KOH-No.) of 50. Aimed at however is a KOH-No. of at least 0.5 or less. 900 additional liters of sodium hydroxide are necessary for the neutralization of 1000 kg fat with 1 M NaOH. Such a method is therefore obviously inefficient for the handling of fats.
Further described possibilities to lower the acidity are the separation of fatty acids through steam distillation (Lurgi) and through selectively effective extracting agents such as for example with an isopropanol/hexane mixture. Alkaline extracting agents will be mentioned for example in DE 199 18 097 A1. The extraction with polyethylene glycols will be described in DE 196 38 459 A1. A chemical conversion of the fatty acids directly into animal fat is an exception. The DE 199 56 599 A1 is concerned with the esterification of ffa in fats with monovalent short chained alcohols in the presence of lipases.
The production of bio diesel using vegetable oils, especially rape oil or sun flower oil, is increasingly preferred by professionals. Several plants have come into production or been built very recently. The oil is completely base-split into the fat components glycerine and fatty acids. Subsequently, the accrued fatty acids are esterified with methanol. Thus generating a fatty acid methyl ester and, as side product, glycerine. The transesterification from fatty acids is basically possible with such apparatus and functions according to the same principle. Further developments, according to DE 697 01 014 D2, concern themselves with the use of ethanol as an esterification reagent.
Thus, it is shown that the previous methods are unsatisfying, especially complicated, extensive and inefficient. This is especially because either an extensive transesterification must be carried out in order to obtain fatty acid methyl esters for example, or the corrosive components in the form of ffa are only removed with great effort. It is therefore the task of the presently claimed invention to further present the previously described method so that the desirable advantages will be targeted.